Influence of Crb2 Additive on the Morphology, Structure, Microhardness and Fracture Resistance of Diamond-Containing Composites Based on Wc‒Co Matrix

By the method of cold pressing followed by vacuum hot pressing, samples of composite diamond-containing materials with a diameter of 10 mm and thickness of 8 mm based on WC–6%Co alloy containing different (from 0 to 10%) contents of chromium diboride, which physical and mechanical properties depend on the composition of the carbide matrix, were developed. The optimal concentrations of chromium diboride ( = 4 %) in the hard alloy composites sintered in a two-stage vacuum hot pressing mode at temperatures Т 1 = 1300 °С and Т 2 = 1400 °С, at which the highest values of physical and mechanical properties of composites ( К I c = 15.4 MPa∙m 1/2 , Н = 14.3 MPa, R bm = 2950 MPa and R cm = 5780 MPa) were achieved. The specified indicators result from the dispersed strengthening mechanism and structure modification (reduction of the average grain size of the carbide phase from 5.6 to 3.4 μm, disappearance of pores at the Co binding phase, formation of inhibitor phase clusters at the interphase boundaries) and the composites phase pattern. Furthermore, all sintered samples containing CrB 2 powder additives in the charge are characterized by a balanced phase distribution and dispersed structure as compared to the sample containing no CrB 2 powder additives.Exceeding 4% of CrB 2 content in a composite material deteriorates its mechanical properties associated with oxidation of tungsten carbide grains and the presence of W=O double bonds on the surface and at grain boundaries of amorphous or nanostructured tungsten oxide.